Lecture 6: Thorax And Spine Flashcards
Prior to vertebrates, the chordates possess a rigid but flexible _________. Vertebrates arise with segmented bony elements with cartilaginous discs in between which are remnants of this structure known as the __________ __________
Notochord
Nucleus pulposus
Early tetrapods have _______ associated with each segment of the trunk. Like the earlier chordates and vertebrates, ____________ movements of the axial skeleton help with locomotion or propulsion
Ribs
Sinuous (side-to-side)
With mammalian tetrapods, there is further differentiation of the regional vertebral segments. Ribs are limited to the __________ region and there are _____ cervical vertebrae in all but a couple of taxa. There is more developed articulation of the occipital portion of the skull with the ________ and there is the odontoid process (dens) on ______. Sagittal __________ of the vertebral column is more prevalent. The sternum is _______ and the thoracic rib cage is generally _______-shaped
Thoracic 7 Atlas (C1) Axis (C2) Flexion Fused Keel
What does the term hominoid refer to?
Apes and humans
Describe the characteristics of the hominoid axial skeleton in terms of the sacrum, caudal vertebrae, and thoracic rib cage
Sacrum is expanded and fused (more segments)
Caudal vertebrae are reduced in number or absent
Conical thoracic rib cage becomes flatter/more broad
Distinct thoracic vertebral region linked to thoracic cavity
Differentiate the terms orthograde and bipedal
Orthograde = upright posture Bipedal = upright walking
What does the term hominin refer to?
Humans and their direct ancestors
Describe characteristics of the hominin axial skeleton in terms of thoracic cavity size/shape, vertebral bodies, sacral angle, and spine curvature
Expansion of thoracic cavity into barrel-shape (no longer conical)
Relative increase in size of vertebral bodies from cervical to lumbar and sacral regions (reflects weight bearing bipedal)
Prominent sacral angle and lumbar lordosis (curvature)
In general, as sacral angle increases, the lumbar convex curvature (lordosis) __________. Does a gorilla have a straighter lumbar region or more curved?
Increases
Gorillas or chimps have straighter lumbar regions and less of a sacral angle
Describe the general function of the spinal column in pronograde/quadrupeds and orthograde/bipeds
Pronograde = suspension bridge with cranium positioned out in front of spinal column
Orthograde = spine acts as an actual column with cranium positioned over it
Describe the Frankfurt plane
In the anatomical position, the skull is oriented so that the inferior margins of the orbits and the superior margin of the external acoustic meatus are horizontal
Allows for standardization of skull position to compare structures among different taxa
Describe the position of the foramen magnum as it relates to quadrupedalism vs. bipedalism
Quadrupedal species have posterior foramen magnum because spinal column extends out behind the head
Bipedal species will have more anteriorly positioned foramen magnum
Compare the thorax and lumbar region of an arboreal quadruped vs. terrestrial quadruped vs. suspensory/climber
Arboreal and terrestrial quadrupeds have narrow thorax and long lumbar region
Suspensory/climbers have broad thorax and short lumbar region
Describe bipedal features in humans including:
Foramen magnum Length of lumbar region Shape of thorax Degree of spinal curvature Degree of sacral angle Coccyx Size of vertebral bodies
Foramen magnum is positioned to hold cranium directly over spine
Relatively short lumbar region
Barrel-shaped thorax
Pronounced spinal curvature
Increased sacral angle
Reduced coccyx/no tail
Progressively larger vertebral bodies that allow weight transmission to lower limb through a columnar structure
The Australopithecines had skulls attaching more ________, a ___-shaped spine with _______ vertebrae that were not likely to be weight-bearing. They had arms that were _________ than their legs and not used for walking. They had ______-shaped pelvis with the femur angled ____. Due to these features, they were likely ___________ bipeds and mostly arboreal.
Inferiorly S Small, lighter Shorter Bowl In Facultative
Homo ergaster/erectus had a ______-shaped rib cage, lumbar _______, and probably ____ lumbar vertebrae. Because of these features, they were likely ________ terrestrial bipeds.
Barrel
Lordosis
5
Habitual
What is the junction point between the cervical and thoracic vertebrae?
Cervicothoracic junction = C7
What palpable skeletal landmark for the human back and spinal column indicates the level of T3?
Scapular spine
The inferior scapular angle is found at the level of what vertebra?
T7
Where is the “transitional vertebra” found in humans?
T12, at the level of the 12th rib
L4 is typically found at the level of what bony landmark?
Iliac crest
Describe general characteristics of cervical vertebrae in terms of size, body shape, foramen size, and characteristics of spinous processes
Smaller, rectangular bodies
Large vertebral foramen
Spinous processes are forked
Also note cervical enlargement for brachial plexus/cervical plexus and transverse foramina for passage of vertebral arteries (blood supply for midbrain)
Describe characteristics of thoracic vertebrae
Facets on transverse processes for ribs
Demi-facets on ribs articulate between the vertebrae
Somewhat longer/larger spinous processes
Larger bodies than cervical, but smaller than lumbar
Smaller vertebral foramen
Describe characteristics of lumbar vertebrae
Large bodies to support more weight
Shorter spinous processes
Shorter transverse processes
Shorter processes to accommodate lumbar lordosis
Describe features of the atlas
Atlas = C1
Superior articular facet articulates with occipital condyles
No body
What is the identifying feature of the axis?
Axis = C2, has the dens aka odontoid process
What aspect of the spinal column allows for passage of spinal nerves?
Intervertebral foramina
What vertebrae appear concave from posterior to anterior?
Cervical and Lumbar
What vertebrae appear convex from posterior to anterior?
Thoracic
What section of the vertebral column has the least degree of mobility and why?
Thoracic region, because it has the rib cage encasing various organs in addition to extensive musculature for upper limb movement, etc.
Cervical and lumbar are more mobile
The intervertebral joints (between vertebral bodies) are primarily maintained by what 3 ligamentous structures?
Annulus fibrosis
Anterior longitudinal ligament
Posterior longitudinal ligament
What is the function of the annulus fibrosis?
Fibrous outer layer of discs - binds the bodies of vertebrae together
What is the function of the anterior longitudinal ligament?
Reinforces the annulus fibrosis
In terms of the ligamentous structures maintaining the intervertebral joints, the spinal cord sits behind the ___________
Posterior longitudinal ligament
Compare the sizes of nuchal ligaments between quadrupeds and bipeds
Quadrupeds have larger nuchal ligaments to suspend the head out in front
What ligament of the human vertebral column contains more collagen than the others?
Ligamentum flava
What ligaments of the human vertebral column are found between transverse processes?
Intertransverse ligaments
How many of each type of vertebrae do humans have?
Cervical = 7 Thoracic = 12 Lumbar = 5 Sacral = 5
What are the 3 parts that make up the sternum?
Manubrium
Body
Xiphoid
Ribs articulate with ________ and _________
Sternum
Vertebrae
Which ribs are considered atypical and why? Are they still considered true ribs?
1 and 2 are atypical because of attachments for neck muscles
11 and 12 are atypical because they are “floating”
YES they are still considered true ribs
What ribs are considered true ribs, aka vertebrocostal?
1-7
What ribs are considered false ribs, aka vertebrochondral, and why?
8-10
They fuse to rib 7 cartilage (they do not have their own costal cartilage)
The head of each rib articulates with 2 ______ on the spinal column
Demi-facets
What aspect of rib structure accommodates intercostal nerves/veins supplying the body wall?
Costal groove
What 2 muscles are associated with rib movement?
Intercostal muscles
Diaphragm contraction
The “pump-handle” movement ribs involves the elevation of ribs and resulting increase in ________________ diameter of the thoracic cavity
Antero-posterior
The “bucket-handle” movement of ribs involves the elevation of ribs and resulting increase in ___________ diameter of the thoracic cavity
Lateral
In terms of relative proportions of manubrium to body of the sternum in primates, apes and humans tend to have a ___________ sternum. What is unique about the sternum components in humans?
Broader
Human sternum components are fully fused by late adulthood
Compare the shape of the thorax of the macaque, chimp, and human
Macaque has scapulae positioned very posteriorly without much invagination; keel-shaped thorax; narrow sternum
Chimp has more invagination and lateral movement of scapula/clavicle (for climbing)
Human has even more invagination and lateral movement of scapula/clavicle (invagination allows for orthograde posture)
Extrinsic muscles of the back are considered __________ and are innervated by the ________ rami of spinal nerves
Hypaxial
Ventral
Intrinsic muscles of the back are considered __________ and are innervated by the _______ rami of spinal nerves
Epaxial
Dorsal
What are extrinsic muscles of the back generally used for?
Movement of the upper limbs and pectoral girdle
What are intrinsic muscles of the back generally used for?
These are mainly postural muscles that support and move the vertebral column and head
The erector spinae group and transversospinalis group are considered to be a part of which type of musculature of the back?
Intrinsic (epaxial)
What part of the transversospinalis group of intrinsic back musculature is the biggest part in the lumbar; in animals with tails: as you go toward the tail it will become the caudalis
Multifidus
Compare the relative size of the erector spinae group in monkeys and humans
In old world monkeys: flares out laterally which reflects quadrupedal adaptation
In humans: smaller with much less flaring
What are 3 important anatomical distinctions from Homo and Pan (baboon) in terms of levator scapulae, rhomboid, and iliocostalis?
Levator scapulae is represented by 2 muscles (atlantoscapularis ant. and post.)
Rhomboid is one muscle and there is a cranial attachment
Highly developed iliocostalis
What are the 2 primary functions of the muscles of the suboccipital region of the posterior neck?
Mainly postural muscles
Aid in extension + rotation at atlantoaxial joint
What two muscles overlay the posterior neck muscles?
Splenius
Semispinalis capitis
What are the 4 muscles of the suboccipital region of the posterior neck?
Rectus capitis posterior major
Rectus capitis posterior minor
Obliquus capitis superior
Obliquus capitis inferior
In terms of important anatomical distinctions in Papio (baboons) from Homo and Pan:
The splenius muscle is very ______ and _______ in Papio, with only a cranial capitis portion, no ________ portion. Deeper posterior neck muscles are similar between Papio and Homo. In Pan, there is an addition unnamed suboccipital muscle passing from C3 to the ________ process of the atlas - this is not present in Homo or Papio
Thick and broad; cervical
Transverse
The muscles of the human pectoral region are innervated by the ______ rami of spinal nerves via branches of the __________ __________
Ventral
Brachial plexus
What muscle of the human pectoral region is responsible for anchoring and stabilizing the clavicle?
Subclavius
What are the 4 muscles of the anterior and lateral abdominal wall? List in order of more anterior/superficial to more posterior/deep
External oblique
Internal oblique
Rectus abdominus
Transversus abdominus
The iliopsoas muscle is formed from what two muscles merging together?
Psoas major
Iliacus
What three pairs of muscles function primarily as flexors of the trunk and/or hip?
The muscles of the posterior abdominal wall:
Iliacus
Psoas major
Psoas minor
What pair of muscles extends to the lumbar vertebral region and also contributes to lateral flexion?
Quadratus lumborum
What are the two important anatomical distinctions in Papio (baboon) from Homo and Pan in terms of pectoral musculature?
Presence of pectoralis abdominus muscles
Presence of pectoralis lateralis and medialis instead of major and minor
What is the general trend from Pan to human in terms of abdominal and pectoral musculature?
Decrease in abdominal and pectoral musculature in bipeds because we do not need to suspend our abdomen above the ground while walking
